Heat olive oil in a large soup pot. Add crabs, ½ cup of the celery, leeks, basil and 6 cloves of the garlic. Sauté, stirring for 5 minutes. Add the tomato sauce, broth, salt and peppercorns.
Bring the liquid to a boil and simmer for 30 minutes, skimming and discarding foam that rises to the top. Drain the broth and discard vegetables. Return broth to soup pot and bring to a simmer.
Mince the last two cloves of garlic. Reduce the broth to approximately 1 ½ quarts. Add carrots, the rest of the celery, and the green beans and cook for about 5 minutes. Add the tomato concasse, spinach, white beans, minced garlic, salt and pepper and simmer an additional 5 minutes.
Cook the pasta shells in boiling, salted water until al dente. Drain, discard any broken shells, and toss the remainder of shells with 1 tablespoon olive oil. Reserve.
Preheat oven to 350 degrees.
Mix the breadcrumbs and butter with crabmeat, salt and pepper in a bowl and mix until thoroughly combined. Spoon the crabmeat mixture into a pastry bag and using a small tip, fill each shell. Coat a baking pan with remaining olive oil and place filled shells in pan. Bake for 10 minutes.